Geographic Range

Antechinus swainsonii is found in south-eastern Australia, ranging from southern Queensland to eastern South Australia, throughout Victoria and New South Wales, and on the island of Tasmania. (Williams and Williams, 1982)

Habitat

A. swainsonii are most commonly found in the moist sclerophyll forests and rainforests of the Australian mainland and Tasmania. A. swainsonii have also been found to inhabit fields overgrown with high grasses but favor any habitat with a dense understory, where most of their activities are restricted (Williams and Williams 1982).

Physical Description

A. swainsonii range in color from dark gray to black. Males and females are sexually dimorphic with an average weight of 65 grams for males, and 41 grams for females (Tasmania PWS 2001; Mammals of Lamington National Park 2001). Males have been reported to reach 130 grams and females 70 grams and it is believed that weight is variable due to availability of resources (Williams and Williams 1982). The average head and body length of A. swainsonii is 128mm and the average tail length is 116mm (Mammals of Lamington National Park 2001).

Reproduction

Competition for mates is extremely high among males. During mating, males have been observed to grab the scruff of the females neck with their teeth, while the females respond by kicking, rolling, and a display of open-mouthed hissing (Williams and Williams 1982). During the breeding season males do not eat, but their body is sustained through gluconeogenic mobilization of body protein (Nowak 2001). This results in deterioration of the male's immune system and death usually within three weeks of copulation. These victims of male "die-off" have been found to have balding patches located on their fur (Tasmanian PWS 2001).

Females breed once, sometime between May and September, and there is considerable evidence that the timing of breeding is correlated with environmental conditions (Williams and Williams 1982). Populations in coastal regions and at lower altitudes have earlier breeding seasons than inland or higher-elevation populations, and populations on the mainland breed earlier than those on Tasmania. Availability of food, temperature, altitude and climate may all play a role in the timing of a population's breeding season.

Gestation lasts 29-36 days. In captivity females show visible signs of enlarged nipples 19 days after copulation; an enlarged, but concealed, pouch at 21 days; and by 23 days, a pouch that is divided into two halves by a ridge (Williams and Williams 1982). The pouch only becomes visible a few days before birth.

A birthing female places herself on all fours with her hindquarters up slightly as the young emerge. A. swainsonii produce supernumery offspring (more offspring than available teats), and some offspring do not reach an available teat, resulting in their death (Williams and Williams 1982).

Young average 4.5mm in length at birth with well developed claws on their forelimbs, and a large circular mouth (Williams and Williams 1982). A sexually mature female has eight teats and litter size ranges from 6-8 young (Nowack 2001). The young are bright pink at birth, but begin to develop fur at 8 weeks with their eyes opening shortly after. The young are left alone in the nest at 10 weeks and begin to eat solid food at 12 weeks. By the 14th week the young are completely weaned and travel outside of the nest attached to their mothers back (Williams and Williams 1982). A. swainsonii develop slowly and are fully mature around 8 months, near the beginning of the next breeding season.

Lifespan/Longevity

Females of the species A. swainsonii usually die after rearing their first litter and males die shortly after copulation (Williams and Williams 1982). Males captured after breeding season still die within the same time period as wild males from their population, but males captured before the breeding season have lived up to two years and eight months (Nowak 2001). Females can live over two years, producing a 2nd litter, but as stated above most die after rearing one litter.

Behavior

A. swainsonii are nocturnal. In captivity however, individuals were observed to be active day and night with periods of extended periods of rest around 12 p.m. and 6 a.m. (Williams and Williams 1982). Fully developed adults are solitary with social interactions occurring during mating and between mother and young. A. swainsonii spend most of their active period feeding, as some individuals have been estimated to eat about 60% of their body weight during the winter months (Nowak 2001). Members of the species seem to have a definite home range, but are not territorial. A. swainsonii construct nests from eucalypt leaves that are balled up in hollow tree trunks or in the dense understory of the forest floor (Tasmania PWS 2001). There is a low mortality rate among young as considerable time and effort is invested maternally in rearing litters (Williams and Williams 2001).

Communication and Perception

Food Habits

A. swainsonii feed mostly on soil invertebrates, as their primary habitat is the forest floor. Along with worms and insects they have been observed eating lizards, small birds, fruit and vegetation (Tasmanian PWS 2001. Mammals of Lammington National Park 2001.) In captivity individuals have been sustained on earthworms, mealworms, grasshoppers, beetle larvae, cockroaches, and small frozen mice. (Williams and Williams 1982)

Contributors

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

insectivore

An animal that eats mainly insects or spiders.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

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The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.